Method of intracranial vascular embolotherapy using self anchoring coils

ABSTRACT

A method of intracranial placement of an embolization coil provided with an anchor to prevent migration of the coil after placement.

FIELD OF THE INVENTION

This invention relates to methods of using occlusive devices for use invascular surgery of the brain.

BACKGROUND OF THE INVENTION

Numerous diseases and conditions of the circulatory system and otherorgans of the body are beneficially treated by the occlusion of bloodvessels. Arteriovenous fistulas, arteriovenous malformations, aneurysmsand pseudoaneurysms, patent ductus arteriosus, gastrointestinalbleeding, renal and pelvic bleeding, and tumors are examples of thenumerous maladies that can be treated by blocking associated bloodvessels. Placement of various substances within the blood vessels is oneof the methods of encouraging the formation of thrombus (clot) whichleads to the complete occlusion of the blood vessels. As early as 1975,coils were successfully used to occlude the renal arteries. Gianturco,et al., Mechanical Devices for Arterial Occlusions, 124 Am. J. Roent.428 (1975). The purpose of the coil is to encourage quick formation of athrombus (a blood clot) around the coil. The coils are currently in usefor a wide range of treatments, and are referred to variously asocclusive coils, embolization coils, or Gianturco coils. They arecommercially available from Cook, Inc. and Target Therapeutics, Inc.

Of the many diseases that may be treated with embolic coils, aneurysmsare of particular interest. Embolization coils of appropriate size forplacement within aneurysms are commercially available from TargetTherapeutics, Inc. Embolization coils made with electrolytic mechanismsfor detachment from the delivery catheter are referred to as GDC's orGuglielmi Detachable Coils. the use of GDC's is illustrated, forexample, in Klein, et al., Extracranial Aneurysms and ArteriovenousFistula: Embolization with the Guglielmi Detachable Coil, 201 Radiology489 (1996). Use of the GDC coils within the brain is illustrated, forexample, in Casasco, et al., Selective Endovascular Treatment Of 71Intracranial Aneurysms With Platinum Coils, 79 J. Neurosurgery 3 (1993).

Because Gianturco and Guglielmi coils are often used to occludeaneurysms in critical areas of the body, it is important that theyremain in place where they are implanted. However, migration of thecoils after placement is a common but dangerous problem encountered withthese coils. Watanabe, Retrieval Of A Migrated Detachable Coil, 35Neuro. Med. Clin. 247 (1995) reports the migration of a coil from aplacement in the superior cerebellar artery into the basilar artery.Halbach, et al., Transarterial Platinum Coil Embolization Of CarotidCavernous Fistulas, 12 AJNR 429 (1991) reports the migration of a coilfrom the internal carotid artery. Migration is particularly common withcoils placed in wide neck aneurysms. The possible migration of coils isa danger that must be considered in every procedure, and actualmigration can be a life threatening complication, since embolization atan unwanted site could occlude a critical blood flow. Migration of thecoil may also represent a failure of the intended therapeutic procedure.

SUMMARY

The method of treating intra-cranial vascular disease comprisesplacement of anchored embolization coils within the intra-cranialvasculature as a means of occluding select portions of the intracranialvasculature. The devices used in the method comprise an anchoring systemattached to a modified stainless steel Gianturco occluding coil. Thecombination creates a mechanical occluding device that can produce alimited size vascular occlusion and can also be used in non-taperingvascular structures in which the possibility of migration is very high.In the brain, such structures may include arterio-venous fistulas,aneurysms and pseudoaneurysms. The anchor is meant to keep the coil inplace and prevent migration. The anchoring system is made of springwires, bars or leafs that extend from the distal or proximal end (orboth) of the embolization coil, and expand against the blood vessel inwhich they are placed, thereby providing additional stability to theembolization coils and preventing migration of the coils.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of the anchored embolization coil housed within adelivery catheter.

FIG. 2 is a view of the anchored embolization coil in its relaxed state.

FIG. 3 is a view of the double anchored embolization coil in its relaxedstate.

FIG. 4 is a view of the anchored embolization coil deployed within ablood vessel near a site of disease.

FIG. 5 is a perspective view of the anchor and embolization coildeployed within a blood vessel.

FIG. 6 is view of the anchored embolization coil deployed within ananeurysm.

FIG. 7 is a schematic diagram of the vasculature of the brain showing atypical placement of a coil.

FIG. 8 is schematic diagram of the vasculature of the brain illustratingthe circle of Willis and arteries supplying the circle of Willis.

DETAILED DESCRIPTIO OF THE INVENTION

FIG. 1 shows a close-up view of the occlusive coil 1 disposed within adelivery catheter 2. The coil may be any of several coils previouslyproposed and used to stuff blood vessels, fistulas and aneurysms, suchas the GDC coils marketed by Target Therapeutics, Inc. or the Gianturcocoils marketed by Cook, Inc. Each coil 1 has a proximal end 22 and adistal end 23. The coils may be pushed out of the delivery catheterusing the pushing wire 24, which may be any suitable guide wire or smallcatheter inserted within the delivery catheter. Pushing and detachmentof the coils can be accomplished by a variety of other methods, such asthe pushrod, pullback of the delivery catheter or other methods. Theconnection between the delivery catheter/push rod assembly may be aquick release type or an easily severable connection, or may be a merecontainment within the catheter. Severable retaining cords,electrolytically severable joints, or miniature quick release orlatching mechanisms may be used. The coil is sized and dimensioned tofit into the target site, which may be an aneurysm such as the aneurysmsillustrated in FIGS. 7 and 8. For intracranial use, the coil will be inthe range of about 2 mm diameter and 10 cm long. The coils are typicallymade of stainless steel, and may be made of other materials such asnitinol, tantalum, platinum, etc. The coils may be coated with athrombogenic coating or may be made with a thrombogenic substance suchas an electro-positive substance. Platinum is an electro-positivesubstance that may be used either as the coil material or as a coilcoating. The coils may fit within standard and commercially availabledelivery catheters, and may be stretched into a straight lineconfiguration to fit within the lumen of small diameter deliverycatheters. Depending on the materials, the coils may be spring biased orprovided with shape memory to assume the shape of a helical coil,rosette shape, pretzel shape or other shape, or an irregular tangle whenunrestrained.

FIG. 1 shows the embolization coil 1 fitted with an anchor 30. Theanchor is affixed distal end 23 of the coil 1, but may also be affixedto the proximal end, or to both ends. The anchor is comprised of twostainless steel wires 31 and 32 which are bent twice to form an anchorhaving a W-Shape. The free legs 33 of the anchor are blunted andreinforced using pieces of a small diameter coil 34 to preventperforation of the vessel wall. While the anchor may be of manyconfigurations, the anchor illustrated in FIG. 1 is furthercharacterized by a shank 35, arms 36 which extend rearwardly from thecrown 37, and flukes comprised of the small diameter coils 34. The arms36 are bent to create a leaf spring arrangement, and the wirescomprising the anchor are spring biased to expand in the open W or Mposition mounted on the shank 35 as shown in FIG. 2. As an alternativeto spring biased stainless steel or other spring metal, superelastic orshape memory alloys and compositions may be used.

As shown in FIG. 2, the embolization coil 1 when unrestrained reverts toits own biased shape (here a coil), and the attached anchor 30 whenunrestrained opens into the W configuration mounted upon the shank 35.The spring biased arms have opened away from the axis of the coil 1, andwill open until they impinge upon the wall of the blood vessel in whichthey are deployed. The wire section forming the shank 35 is reinforcedwith small support 38 which helps keep the shank oriented in properrelation to the coil. FIG. 3 illustrates that the coil may be providedwith an additional anchor 30p at the proximal end of the coil, thusforming an embolization coil having anchors at both ends of the coil.Another feature illustrated in FIG. 3 is the thread attachments 39 (alsocalled strands or tails) which are fastened to the coil 1 at variouspositions along the length of the coil. These threaded attachmentsfurther promote the formation of thrombus around the coil. The threadedattachments may be added to any embodiment of the anchored embolizationcoil, and may be made of Dacron, polyester, silk or wool or othersuitable material.

FIG. 4 shows the embolization coil 1 with an anchor deployed within ablood vessel 41 with a diseased site 42. The diseased site may be ananeurysm, fistula or other disease distal to the site of deployment, butin the case of FIG. 4 a fistula is chosen to illustrate the operation ofthe coil. The anatomy shown in FIG. 4 is an artery 43 and a vein 44which are connected via the fistula or arterio-venous shunt 45. Theartery and vein should not be directly connected, but should beindirectly connected through a capillary bed. The fistula 45 can be theresult of injury, poor healing after surgery, or congenital defect. Inany case, the abnormal connection through the fistula 45 should beoccluded. To accomplish this, the anchored embolization coil 1 is placedvia the delivery catheter 2 into the artery 43 just upstream in theblood flow from the fistula 45. After release from the delivery catheterthe coil is transformed by virtue of its spring bias into the helicalshape, and fills a substantial portion of the blood vessel 41. Theanchor 30 has also opened toward its unrestrained shape to the extentallowed by the blood vessel wall. The arms of the anchor are urged byspring force into contact with the blood vessel wall. The slight forceapplied by the spring bias of the anchor 30 on the wall anchors theembolization coil 1 into place. The anchor may bend to conform to theinternal diameter of the blood vessel. The free legs 33 and the arms 36define a semicircular arc across the lumen of the blood vessel. Inaddition to the placement of coil 1, the space upstream of the coil andanchor can also be filled with additional released coil turns. Thus, thecoil conglomerate can be made more compact improving the stabilizationof the device further.

When deployed within a generally cylindrical vessel such as the artery43, the anchor will bend to conform to the inner surface of the artery,as illustrated in FIG. 5. FIG. 5 shows a perspective view of the arteryand anchor within the artery. The anchor 30 has arched into conformancewith the inner surface of the artery, in this case taking on the shapeof an M or W mapped onto the inside of the generally cylindrical shapeof the blood vessel. Because the anchor arches around the wall of theblood vessel, the central portion of the lumen which is co-extensivewith the anchor is left unfilled, making it possible to either applyadditional occluding material in the proximal space 46 in front of theembolization coil, or leaving some branch vessel in the spaceun-occluded while using the space to anchor the embolization coil. Thisas a feature not encountered with Amplatz spiders or similar devices.

FIG. 6 shows the embolization coil 1 with an anchor deployed within ananeurysm 20 at the bifurcation of the common carotid artery 4 into theinternal carotid artery 5 and external carotid 7 artery in the neck.This aneurysm is known as a bifurcation aneurysm. The embolization coilhas transformed by virtue of its spring bias into the irregular shapeshown, and fills a substantial portion of the aneurysm 20. The anchor 30has also opened toward its unrestrained shape to the extent allowed bythe aneurysm wall. The arms of the anchor are urged by spring force intocontact with the aneurysm wall. The slight force applied by the springbias of the anchor 30 on the wall anchors the embolization coil 1 intoplace, and prevents the coil from being washed out of the aneurysm bythe high velocity blood flow at the bifurcation.

As can be seen by inspection of FIGS. 4 and 6, in a vessel with adiameter smaller than that of the unconstrained device, the device willbe partially compressed. Consequently, the anchor will lean against thewall at multiple points resulting in a stable position. To achieve agood fixation the largest unconstrained diameter of the anchor ispreferably equal to or slightly larger than twice the diameter of thevessel to be occluded. Sufficient anchoring power can be achieved withan anchor having an unrestrained diameter of the vessel, where theanchor is made of 0.010 inch stainless steel wires and the coil isanchored in high flow vessels. In moderate flow vessels, anchors made of0.0075" stainless steel wire and having an unrestrained expandeddiameter of slightly larger than the diameter of the target vesselprovide adequate anchoring strength. The thickness, open diameter andlength of the anchors may be varied to accommodate the numerous sizeblood vessels within the human body, as well as the fragility of theaneurysm or vessel wall.

FIGS. 7 and 8 show the vasculature of the brain in sufficient detail tounderstand the invention. The brain 3 is supplied with blood through thecarotid and the vertebral arteries on each side of the neck. Theimportant arteries include the common carotid artery 4 in the neck,which will be the most common access pathway for the stent, the internalcarotid 5 which supplies the opthalmic artery 6. The external carotid 7supplies the maxillary artery 8, the middle meningeal artery 9, and thesuperficial temporal arteries 10 (frontal) and 11 (parietal). Thevertebral artery 12 supplies the basilar artery 13 and the cerebralarteries including the posterior cerebral artery 14 and the circle ofWillis indicated generally at 15. The siphon 12a of the vertebral arteryappears in the intra-cranial vasculature on the vertebral approach tothe Circle of Willis. Also supplied by the internal carotid artery arethe anterior cerebral artery 16 and the middle cerebral artery 17, aswell as the Circle of Willis, including the posterior communicatingartery 18 and the anterior communicating artery 19. The siphon 5a of theinternal carotid artery 5 appears in the intra-cranial vasculature onthe carotid approach into the Circle of Willis. These arteries typicallyhave an internal diameter of about 1 mm to 5 mm, most commonly from 2-4mm. The methods and devices described herein allow access to thesearteries and placement of occlusive coils in these arteries or into theaneurysms affecting these arteries. In FIG. 7, the insertion catheter 2and occlusive coils 1 are shown threaded through the common carotidartery 4 and the internal carotid artery 5, with the coil extending intothe aneurysm 20 illustrated in the opthalmic artery 6.

FIG. 8 shows the same blood vessels in a schematic view that betterillustrates the Circle of Willis and the arteries which supply thisimportant anatomic feature. The Circle of Willis 15 is a ring ofarteries connecting the internal carotid arteries and the basilar artery(and hence the left and right vertebral arteries) to the anteriorcerebral arteries 16, middle cerebral arteries 17 and posterior cerebralarteries 14. The system provides a redundant supply of blood to thecerebral arteries. The carotid siphon 5a, which forms an integral partof the internal carotid artery 5, is more clearly visible in this view.Aneurysms, fistulas, AVM's and tumors occurring inside the brain, in theintracranial portion of the carotid arteries, vertebral arteries (andthe portions of those arteries distal to the siphons) and basilarartery, in the circle of Willis or even deeper within the brain may betreated with the occlusive coils and delivery systems described above.FIG. 8 shows an exemplary use in which a delivery catheter 2 is insertedthrough the aorta into the vertebral artery, the basilar artery, andinto the Circle of Willis 15 to treat an aneurysm 20 which has occurredin this illustration at the bifurcation 21 where the basilar arteryfeeds into the right and left posterior cerebral arteries 14. Theaneurysm is treated with occlusive coils 1 which are inserted into theaneurysm and delivered in place through the distal tip of the deliverycatheter 2.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. It isexpected that the devices will used to treat a variety of conditionswithin the intracranial vasculture in addition to those set forth aboveOther embodiments and configurations may be devised without departingfrom the spirit of the inventions and the scope of the appended claims.

We claim:
 1. A method of treating vascular disease in an intracranialblood vessel comprising:providing an anchored coil for occluding theintracranial vasculature at or near the site of vascular disease withinthe intracranial vasculature, said coil being provided with an anchor inthe shape of an M or W, said coil being formed of wire and having anunrestrained expanded width exceeding the diameter of the intracranialblood vessel; inserting the anchored coil into the intracranial bloodvessel at or near the site of vascular disease and allowing the anchorto expand toward its unrestrained expanded width so as to come intoengaging contact with the blood vessel and thereby anchor the coil inplace within the intracranial blood vessel.
 2. The method of claim 1,further comprising the step of inserting the anchored coil into theintracranial blood vessel through a percutaneous access pathway from aremote site in the vasculature of the body.